104 LINK ON THE FLUIPS OF PLANTS. 



EXPERIMENTS ON THE ABSORPTION AND CIRCULATING 

 FLUIDS OF PLANTS. 



BY H. F. LINK, PROFESSOR OF BOTANY, BERLIN. 



TREVIRANUS is of opinion, that the sap of plants flows between the 

 cells, meaning the interstices between these, an opinion adopted by 

 M. Kieser, and also as it would appear by M. De Candolle. It is 

 true, indeed, that the sap may be supposed in this manner to diffuse 

 itself freely in every part of the plant j but then the bark and pith, 

 from the looseness of their cellular texture, ought to afford more 

 facilities for the flow of the juices than the wood, and this does not 

 accord with the following observations. 



It has been customary to tinge the water introduced into plants, 

 for the purpose of experiment, with ink, tincture of litmus, of Brazil 

 wood, and the like. The ink is well known to contain the gallate 

 and tannate of iron suspended in water by means of gum ; and it is 

 very possible that other vegetable colouring matters may be similarly 

 suspended in water without being dissolved. The outer rind 

 (epidermis) of plants, and vegetable membrane in general, is capable of 

 filtering coloured liquids, and preventing the colouring matters from 

 entering into the vessels. From this we may account for experi- 

 ments in which coloured fluids do not enter into the vessels, or at 

 least do not appear when these are cut. In order to avoid such in- 

 convenience, it is requisite to effect a precipitation in the vessels 

 themselves, and to produce a precipitate of a well marked colour, 

 such as may not be confounded with the colours naturally produced 

 in a plant. 



I took therefore several healthy plants in pots, such as are com- 

 monly found in green houses, a Rhagodia, a Bigonia, a Stilydium, 

 and a Hermannia. I put the pots containing these plants in vases 

 filled with a solution of the cyanuret of potass and iron, made with 

 one part of cyanuret and thirty-two parts of water, in which I 

 allowed them to remain for an entire week. The plants watered in 

 this way continued quite healthy. I then removed the vases, and 

 substituted others filled with a solution of sulphate of the oxyde of 

 iron in thirty-two parts of water, taking previous care to wipe the 

 pots dry. I left them in these vases for twenty-four hours, when I 

 cut the plants, and, on examining the interior parts with the micro- 



* Translated from the French by the Editor. 



